1. Technical Field
The following description relates to a plasma source. For example, the following description relates to a plasma source for a substrate, for solving the non-uniformity of a density of plasma caused by the standing wave effect generated according to large sizing of a substrate, by installing a plurality of impedance boxes for current control at an outer circumference surface of a source electrode, which is a plate shape antenna, such that the plurality of impedance boxes are grounded to a vacuum chamber, and making the impedances of the respective impedance boxes separately controllable.
2. Description of the Related Art
In general, plasma, an ionized gas, is the fourth state of matter that is not solid, liquid, and gas. Free electrons, positive ions, neutral atoms, and neutron molecules exist within plasma and incessantly interact with each other. The control of each component and concentration of free electrons, positive ions, neutral atoms, and neutron molecules is of significance. In engineering aspects, plasma is regarded as being in the field of gas, which can be formed and controlled by an external electric field.
A conventional plasma generating apparatus is described below.
As illustrated in FIG. 1, the conventional plasma generating apparatus is constructed to generate plasma 18 based on capacitive coupling within a vacuum chamber 10, by installing two plate electrodes that are a source electrode 11 and an Electrostatic Chuck (ESC) (or a susceptor) 12 spaced a predetermined distance apart up/down within a central region of a substrate 17, then placing the substrate 17 on a top surface of the ESC 12, and then applying a Radio Frequency (RF) to the source electrode 11 and the ESC 12 from the external to form a strong electric field between the source electrode 11 and the ESC 12. Non-described reference numerals 13, 14, 15, and 16 denote a source RF, a bias RF, a source matcher, and a bias matcher, respectively. The thus generated plasma is used for deposition, etching, etc. in a Liquid Crystal Display (LCD) device or solar light device.
In recent years, a substrate is in trend of large sizing. Because of this, an antenna for generating plasma should increase in size. However, according to the conventional art illustrated in FIG. 1, because the plate shape antenna, the source electrode 11, is in floating, a boundary condition is not fixed. Due to this, the non-uniformity of an electric field between a center and edge of the source electrode 11 is generated and thus, as illustrated in FIG. 2, a Radio Frequency (RF) power delivered to the edge of the source electrode 11 decreases. This non-uniformity of the electric field results in the standing wave effect, thus causing a problem of deteriorating the uniformity of plasma generated at the edge of the plate shape antenna 11.